Skateboards and certain types of roller skates are supported by wheeled truck assemblies. Although the invention (including its background) is described in connection with skateboards, those skilled in the art will recognize that the invention may be used for other types of devices, such as certain types of roller skates, street lugs, and others.
In a typical configuration, a skateboard has an elongated deck with a longitudinal axis. The deck is supported by two wheeled truck assemblies that are attached to the underside of the deck. In these typical configurations, one truck assembly is attached relatively near each end of the skateboard deck. The wheeled truck assemblies typically include an axle that is substantially orthogonal to the longitudinal axis of the skateboard deck. The truck assembly (including the axle) is typically symmetrical about the longitudinal axis of the skateboard deck. A wheel is attached to each end of the axle.
The wheeled truck assembly typically includes a pivoting mechanism that changes the orientations of the axle with respect to the skateboard deck. Such pivoting provides directional turning capability, allowing the rider to provide directional control to the skateboard. An exemplary truck assembly including a pivoting mechanism is shown in U.S. Pat No. 5,853,182 to Finkle. In accordance with the teaching of that patent, an axle assembly is supported on an elastomeric bumper, which in turn is supported on an angled shaft. As the skateboard deck is tilted, the bumper twists, causing the axle of the truck assembly to tilt and turn. The degree of hardness of the elastomeric material forming the bumper affects the relationship between the turning of the truck axle and the pressure applied by the rider to tilt the skateboard deck. Generally, a harder elastomeric material provides less turning of the axle direction for a given pressure on the skateboard deck than does a softer elastomeric material. Thus, the harder elastomeric material requires greater pressure to achieve the same degree of turning.
The range of turning movement available with the elastomeric bumper is limited by the tensile strength of the elastomeric material as the bumper is twisted. In certain circumstances, somc riders may desire a greater degree of turning than is available with such elastomeric bumpers. This is particularly true for riders of exceptionally long skateboards (for example, 3-4 feet (0.9-1.2 m) in length).
Some skateboard riders desire a high degree of predictability to the tilting pressure required to execute particular turns. Because of inherent variations in the compounds used for the elastomeric bumper. the turning performance of skateboard trucks using such elastomeric bumpers may not have the desired degree of predictability.
An additional desired feature for some skateboard riders has been to adjust the degree of turning achieved with a particular application of force, or conversely to adjust the amount of force necessary to achieve a particular turning angle for the axle. Such adjustment is possible with the skateboard trucks incorporating an elastomeric bumper by substituting a bumper having a different elastomeric hardness. Such substitution requires disassembly of the truck, a time-consuming activity that typically requires one or more tools. In addition, because of the inherent differences in the performance of different elastomeric compounds from which the bumpers are made, the desired level of turning performance is not always achieved on the first substitution, thereby requiring repeated disassembly and reassembly of the truck.
Some have suggested using springs to control the degree of turning relative to a particular amount of tilting force applied to the skateboard deck. However, such configurations incorporate separate springs on each side of the axle, which springs must be carefully adjusted to achieve balanced performance between the two sides. Changing the tension on such springs to alter the performance of the skateboard is very difficult.
The present invention is a truck assembly for skateboards and similar devices that provides a large turning range for the axle, provides a highly predictable turning performance, and provides tool-less adjustment of the turning performance.
It is an object of the present invention to provide a wheeled truck assembly for a skateboard that permits the skateboard to have a small turning radius.
It is an object of the present invention to provide a wheeled truck assembly with a large axle turning range.
It is an object of the present invention to provide a wheeled truck assembly that permits a sharp turning angle for the axle.
It is an object of the present invention to provide a wheeled truck assembly having a highly predictable turning performance.
It is an object of the present invention to provide a wheeled truck assembly having a stable turning performance.
It is an object of the present invention to provide a wheeled truck assembly having an adjustable turning performance.
It is an object of the present invention to provide a wheeled truck assembly in which the turning performance may be adjusted without the use of tools.
It is an object of the present invention to provide a wheeled truck assembly that provides adequate clearance for the use of large wheels.
It is an object of the present invention to provide a wheeled truck assembly that includes a turning mechanism having cam faces that are urged against each other by a spring member and an elastomeric element to control the pressure between the cam faces.
This invention has several features, no single one of which is solely responsible for its desirable attributes. Without limiting, the scope of this invention as expressed by the claims that follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled, xe2x80x9cDETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS,xe2x80x9d one will understand how the features of this invention provide its benefits which include, but are not limited to, selective control of turning of a skateboard and improved performance.
The truck assembly of the present invention includes an axle housing, a base, and a kingpin connecting the axle housing and base.
The kingpin holds the axle housing and a base surface of the base a predetermined distance apart. The truck further includes a turning mechanism between the axle housing and base, around the kingpin. The turning mechanism includes opposed cam surfaces that are angled along the axis of the kingpin to control the rotation of the axle housing about the kingpin axis off of center position, and to tend to return the axle housing to its center, straight-ahead position. In particular, the turning mechanism includes an axle housing cam face on the axle housing, with the axle housing cam face having at least two cam surfaces. A cam element between the base and the axle housing includes a cam face with at least two cam surfaces that engage the cam surfaces of the axle housing cam face. A resiliently compressible bushing spaces the cam face of the cam element from the base.
The truck assembly of the present invention additionally includes an adjustment mechanism for adjusting the pressure with which the opposed cam faces oppose one another. The adjustment mechanism includes an adjustment surface on the base of the truck assembly with two or more adjustment points, each a different distance from the base surface along the direction of the kingpin. An adjustment ring surrounds the kingpin, between the base surface and the turning mechanism. The adjustment ring includes adjustment lobes that engage the adjustment surface on the base, so that positioning the adjustment lobes at different ones of the adjustment points positions the adjustment ring at different distances from the base surface.
In one embodiment, the turning mechanism has an elastomeric element and a spring member that at least partially encloses the elastomeric element. The cam surfaces are urged against each other by the spring member and the elastomeric element to control the pressure between the cam surfaces. The elastomeric element is in the form of a hollow cylinder through which the kingpin extends. This elastomeric element sets the maximum pressure between the cam surfaces. The spring member provides controlled variation in pressure between the cam surfaces.